Rain affects gender ratio of African buffalo

The amount of rain affects whether more male African buffalo, than female buffalo, are born in Kruger National Park.

The amount of rain affects whether more male African buffalo, than female buffalo, are born in Kruger National Park, scientists said. Data collected from more than 200 buffalo calves and 3,000 fetuses showed an increased proportion of male African buffalo were born during the rainy season, said researchers from Wageningen University, The Netherlands.

The data, collected between 1978 and 1998 suggests ejaculate volume, sperm motility and proportion of normal-shaped sperm decrease significantly during the dry season, when more females are born. "Gender ratios were male-biased during wet periods and female-biased during dry periods, both seasonally and annually," researcher Pim van Hooft wrote in a recent edition of BMC Evolutionary Biology.